I realized: you’re thinking of news headlines in English. That doesn’t apply to book titles.
You could omit articles in chapter titles if you wanted, but it would change the tone of the ToC: Is this a rigid formal book (no articles) or an easy-to-read introduction (with articles)?
You could omit articles in chapter titles if you wanted, but it would change the tone of the ToC: Is this a rigid formal book (no articles) or an easy-to-read introduction (with articles)?